Hitherto, silver, copper, and other antimicrobial metals supported in apatite, zeolite, glass, zirconium phosphate, silica gel, or the like have been known as inorganic antimicrobial agents. In comparison to organic antimicrobial agents, these inorganic antimicrobial agents have high safety and do not volatilize or decompose, thus having characteristics of a long-lasting antimicrobial effect and excellent heat resistance. Therefore, antimicrobial resin compositions obtained by mixing the antimicrobial agents and a variety of polymer compounds are used for a variety of uses in the form of antimicrobial-processed products that are processed into a fibrous shape, a film shape, a variety of compacts, and the like.
Among them, a vitreous antimicrobial agent containing antimicrobial metals, such as silver, copper, and zinc, that is, antimicrobial glass is mixed in antimicrobial resin compositions for a variety of uses and used taking advantage of the characteristics that the granularity of the glass, the refractive index, the elution properties of the antimicrobial metals, and the like can be easily controlled according to the purpose (for example, refer to Patent Literature 1, 2, and 3).
12 mesh (aperture size 1.68 mm)-passable particulates that are used to inhibit the generation of aquatic microbes, such as slime and algae that generate in cooling towers, water tanks, pools, solar systems, irrigation water, and the like (for example, refer to Patent Literature 4), antimicrobial flake-shaped glass that is used as a paint or lining materials for painting water-processing facilities, livestock-producing facilities, food factories, and building materials, or a reinforcing filler of resin compacts, such as air conditioners, and the like so as to effectively inhibit the generation and propagation of microbes, fungus, and algae at the corresponding sites (for example, refer to Patent Literature 5), borate-based or phosphate-based water-soluble silver glass which is used to suppress the propagation and sterilize microorganisms, such as microbes, filamentous fungi, yeast, and algae, that propagate in water inside tanks used in ultrasonic humidifiers, which is made into a bead shape or a certain form that is maintained and used in water inside tanks, and which uniformly contains monovalent silver ions (for example, refer to Patent Literature 6), glass particles with a particle diameter of 1 mm to 50 mm which are filled in a column installed in a water-supplying system or a circulating system of an apparatus for purifying bathwater, and through which bathwater passes (for example, refer to Patent Literature 7), silver ion-containing soluble glass powders with a dissolution rate of 0.005 mg/g/Hr to 50 mg/g/Hr which are accommodated in a cartridge filter for obtaining deodorized and sterilized potable water and the like used in restaurants, houses, and the like are suggested as the vitreous antimicrobial agent for water processing.
Furthermore, a method in which an antimicrobial agent is brought into contact with water used for washing that is supplied to a washing tub so as to supply, for example, silver ion-based antimicrobial components to the washing tub in order to suppress the generation of bad odors of laundry, such as clothes (for example, refer to Patent Literature 9), and antimicrobial glass for carrying out an antimicrobial treatment using silver ions during or after washing of articles to undergo an antimicrobial treatment in which the maximum diameter (t1) is within a range of 1 mm to 50 mm, and the amount of eluted silver ions is within a range of 0.5 mg/(g·24 Hrs) to 100 mg/(g·24 Hrs) (for example, refer to Patent Literature 10) are known as antimicrobial agents for washing. However, the antimicrobial glass has a problem of discoloration, and Patent Literature 10 suggests using at sites which are not visible or coating with a colored coating material as the countermeasures. When the antimicrobial glass is installed so as not to be visible, it is difficult for general consumers to ascertain the effective duration (service life) of the antimicrobial agent, and, even when the antimicrobial agent is installed so as to be visible, it is necessary for the antimicrobial agent itself to exhibit an appropriate change in appearance in order to allow general consumers to ascertain the effective duration of the antimicrobial agent by a simple method of measuring by hand, checking the appearance, or the like but there has been no technique that is intended to allow general consumers to ascertain the effective duration (service life) by a simple method.
Methods of manufacturing silver glass that elutes silver ions and can be used as antimicrobial glass include a method of manufacturing granular glass having an average particle diameter of 0.1 μm to 10 mm (for example, refer to Patent Literature 11), a method of manufacturing silver ion-containing glass for which an alkali metal salt of boric acid is used as the raw material (for example, refer to Patent Literature 11), and the like, but these methods are not intended to allow general consumers to ascertain the effective duration (service life) by a simple method.
In the case of use in water-processing, when a powdered antimicrobial agent is used, generally, there are problems in that the water becomes muddy, and thus cannot be recovered. Therefore, granular products are preferred as a water-processing antimicrobial agent. However, silver glass obtained by manufacturing methods according to the general conventional art has a cullet form (crushed glass) or a flake shape and an uneven granularity or shape, and thus, in practice, there is room for further improvement when the silver glass is packed in a bag and used, such as the filling properties, the risk of scratching and the like due to sharp-edge portions, the tearing of the bag during processing and use, furthermore, the susceptibility to clogging caused by an increase in the filling density which leads to degradation of the water permeability, and the like. Meanwhile, fusion molding can also be used to make the glass into a certain shape, such as glass beads, but the costs for the molding process are high, and there is a limitation on the shapeable glass compositions, and therefore it is difficult to obtain a uniform molded product in a glass composition having an appropriate solubility.
Considering the applications in the home, such as the provision of microbe resistance and deodorization of water used for washing, the provision of microbe resistance to bathwater, and the inhibition of algae growth in a water tank, the appropriate amount of the antimicrobial agent used is several tens of grams per each use for the handling properties or detection of the service life. Antimicrobial products obtained by filling several tens of grams of the antimicrobial agent in a knitted fabric, non-woven fabric, or other bag can be preferably used for the above uses, and the effective duration can be easily determined by detection of the appearance or measuring by hand. When the particles of the antimicrobial agent do not allow passage of water when manufacturing such a product, it is difficult to obtain the antimicrobial effect. In addition, when the weight of one particle is more than 1 gram, there are problems in that it is difficult to adjust the amount of the antimicrobial agent filled in a bag to be constant, a large variation is caused in the amount of the antimicrobial agent filled by an automatic filling machine, and the like. There has been no example of silver glass that is appropriate for the use of water processing.